<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        /* `+`  选择下一个(紧挨着的)符合条件的兄弟元素 */

        .li1+li {
            background-color: red;
        }

        /* `~` 选择后边所有符合条件的兄弟元素 */
        .li1~li{
            background-color: orange;
        }


        .list{
            padding: 0;
            list-style: none;
            width: 1160px;
            margin: 0 auto;
            overflow: hidden;
            background-color: gray;
        }

        .item{
            float: left;
            width: 275px;
            height: 200px;
            background-color: red;
            /* margin-right: 20px; */
        }
        /* .item.mr0{
            margin-right: 0;
        } */

        .item+li{
            margin-left: 20px;
        }
    </style>
</head>

<body>
    <ul>
        <li class="li1"></li>
        <!-- <p>不凡学院</p> -->
        <li class="li2"></li>
        <li class="li3"></li>

    </ul>

    <ul class="list">
        <li class="item"></li>
        <li class="item"></li>
        <li class="item"></li>
        <li class="item mr0"></li>
    </ul>
</body>

</html>